The present invention relates to an image forming method for obtaining a color image by exposing a photosensitive material with light of three colors.
A heat developable photosensitive material for use as an image recording material has been well known in the art. Heat developable photosensitive materials and processes for such materials are described, for example, in Photographic Industry's issue on "Basic Nonsilver Salt Photography," Corona Publishing Co., 1982, pp. 242-255, Video Information, April 1978, p. 40, and Neblett's Handbook of Photography and Reprography, 7th ed., Van Nostrand, Reinhold & Co., pp. 32-33.
In addition, there have been proposed many methods for obtaining color images by heat developing.
For instance, there have been proposed a method in which a mobile dye is released by heating in the form of an image, and the mobile dye is transferred onto a dye fixing material containing a mordant by the use of a solvent such as water, a method in which the mobile dye is transferred onto a dye fixing material by means of an organic solvent having a high boiling point, a method in which the mobile dye is transferred onto a dye fixing material by means of a hydrophilic solvent incorporated in the dye fixing material, and a method in which a mobile dye of a heat diffusion or sublimatory type is transferred onto a dye acceptor such as a substrate. (See as examples, U.S. Pat. Nos. 4,463,079, 4,474,867, 4,478,927 and 4,507,380, Japanese Laid-Open Patent Publications Nos. 58-149046, 58-149047, 59-1522440, 59-154445, 59-165054, 59-180548, 59-168439, 59-174832, 59-174833, 59-174834 and 59-174835.)
As a device for carrying out image formation of the above-mentioned type, there has been proposed an image forming device as disclosed, for example, in Japanese Laid-Open Patent Publication 59-75247 in which, following exposure in an exposing unit, a color image is transferred to a heat developable photosensitive material by the use of an exposing head, the photosensitive material is sent to a heat developing unit, the heat developable photosensitive material subjected to heat developing with an image-receiving material fixed thereto is sent to a transfer unit, and the image is thermally transferred onto the image-receiving material in the transfer unit.
Further, there has been proposed an image forming device in which, following the application of an image forming solvent to at least one of a photosensitive material and an image-receiving material, heat developing and heat transfer are executed simultaneously by superposing the photosensitive material and the image-receiving material.
Image forming devices may be generally divided into two categories, namely, the frame sequential system and the dot sequential system, depending upon the mode of scanning used for exposing the photosensitive material.
In the frame sequential system, a photosensitive material is sequentially exposed by driving light-emitting elements provided for each of the three primary colors. In this system, there are required at least three exposure scannings to form a color image, as a result of which the required exposure time is long.
In the dot sequential system, three light-emitting elements corresponding to the three primary colors are driven simultaneously, and the emitted radiations are combined to expose the photosensitive material, whereby exposure can be completed within a short time.
Further, in the dot sequential system, information for the three colors is stored temporarily in a buffer memory for one image plane portion, the information is read simultaneously on a dot-by-dot basis for three colors from the memory to drive the light-emitting elements, and the radiations emitted from the respective light-emitting elements are optically combined. Consequently, there is a problem in that a memory of large capacity is required, leading accordingly to a high cost of production.